Particle size measurement INDEX

This is a Fredholm integral equation of the first kind. The regularized solution to this equation has been applied to the measurement both for the moments and the size distribution of a wide range of latices [46]. K has been given by van de Hulst [45] in terms of particle size/refractive index domain. Mie theory applies to the whole domain but in the boundary regions simpler equations have been derived. 

Particle Size, Polydispersity Index, and Zeta Potential Measurements... 

Particle size, polydispersity index, and zeta potential measurements of mannosylated liposomes are determined by Zetasizer nano ZS-90. 

The sums in Equation 7.31 involve the summation over the individual realizations of particle velocities (index j) in a pre-defined directional class (index k) and size class (index i). The summation over the particle size classes (index i) include the appropriate particle size-dependent cross-section of the measurement volume for each directional class (Equation 7.29). It should be stated that the use of a mean velocity either in a directional class or a size class is not appropriate to determine the particle concentration, since the mean velocity may become zero or close to zero resulting in an infinite concentration as pointed out by Hardalupas and Taylor (1989). 

Here t is the particle residence time in the measurement volume, Vol(Di) is the particle size-dependent volume and N is the number of samples in one particle size class (index i). As demonstrated by Qiu and Sommerfeld (1992), the particle residence time or burst length cannot be accurately determined for noisy Doppler signals. Hence this alternative method is not very reliable and yields considerable errors in particle concentration measurements. 

The Fraunhofer theory was the basis for the first (approximating) optical model for particle size measurement. For particles with a diameter dp larger than the wavelength A, Fraunhofer diffraction is often assumed [105]. However, only scattering by opaque particles or particles with a large real refractive index ratio m, i.e., the ratio of the refractive index of scattering particles to that of the fluid. 

In the early days of particle size measurement, the advantage of this relatively simple theory was that it usually describes the scattering patterns of transparent particles of a few micrometers in size in liquid media better than Fraunhofer theory. Similar to the Fraunhofer theory, the anomalous diffraction theory requires no exact knowledge of the refractive index, but it should not be used for opaque particles. 

Miles BH, Sojka PE, King GB (1990) Malvern particle size measurements in a media with time varying index of refraction gradients. Appl Opt 29(31) 4563-4573... 

Source sampling of particulates requites isokinetic removal of a composite sample from the stack or vent effluent to determine representative emission rates. Samples are coUected either extractively or using an in-stack filter EPA Method 5 is representative of extractive sampling, EPA Method 17 of in-stack filtration. Other means of source sampling have been used, but they have been largely supplanted by EPA methods. Continuous in-stack monitors of opacity utilize attenuation of radiation across the effluent. Opacity measurements are affected by the particle size, shape, size distribution, refractive index, and the wavelength of the radiation (25,26). 

Fraunhofer rules do not include the influence of refraction, reflection, polarization and other optical effects. Early Iziser particle analyzers used Fraunhofer approximations because the computers of that time could not handle the storage cuid memory requirements of the Mie method. For example, it has been found that the Fraunhofer-based instrumentation cannot be used to measure the particle size of a suspension of lactose (R.I. = 1.533) in iso-octane (R.I. = 1.391) because the relative refractive index is 1.10, i.e.- 1.533/1.391. This is due to the fact that diffraction of light passing through the particles is nearly the same as that passing around the particles, creating a combined interference pattern which is not indicative of the true... 

The distribution of molecular weights of each generation was determined from measurements on about 50 molecules, with results shown in Figure 12.19 (the weight fraction is the percent dendrimer in each interval of molecular weight under consideration). Based on these distributions, the polydispersity index (.MJMa) of G5 to G10 can be calculated, with results shown in Table 12.1 [39], They are all less than 1.08, which means that the particle size distribution is very uniform for each generation. 

The efficiency of a column can be assessed in a similar manner to that described for HPLC and values for the resolution index of two solutes, the number of theoretical plates and the height equivalent to a theoretical plate may also be calculated. Although it is easier to measure gas pressure, it is the actual gas flow, which is affected by the particle size and compression of the packing, that should be used in column assessment investigations. 

Phase functions can also be used to measure the size and refractive index of a microsphere, and they have been used by colloid scientists for many years to determine particle size. Ray et al. (1991a) showed that careful measurements of the phase function for an electrodynamically levitated microdroplet yield a fine structure that is nearly as sensitive to the optical parameters as are resonances. This is demonstrated in Fig. 21, which presents experimental and theoretical phase functions obtained by Ray and his coworkers for a droplet of dioctylphthalate. The experimental phase function is compared with two... 

---